1. Field of the Invention
The present invention relates to a carbon nanotube-based device and a method for making such a carbon nanotube-based device.
2. Description of Related Art
Carbon nanotubes are very small tube-shaped structures having the composition of a graphite sheet rolled into a tube. Carbon nanotubes produced by arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima titled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56–58). Carbon nanotubes have very high electrical conductivity along a length thereof and are chemically stable, and have very small diameters (less than 100 nanometers) and large aspect ratios (length/diameter). Due to these and other properties, it has been suggested that carbon nanotubes can play an important role in fields such as microscopic electronics, materials science, biology and chemistry. Recently, a few electronic components based on a single carbon nanotube have been made in laboratories, such as a field effect transistor, a logical circuit, and a memory. For example, a transistor is reported in an article by Sander J. Tans et al. titled “Room-temperature transistor based on a single carbon nanotube” (Nature 393–49, 1998).
Although carbon nanotubes promise to have a wide range of applications, better control over their growth patterns and architectures is desired. Chemical vapor deposition has been used to grow aligned nanotubes vertically on catalyst-printed substrates. Additionally a method for controlling the growth of aligned nanotubes in several directions on a substrate at once in a single process was reported in an article by B. Q. Wei et al. titled “organized assembly of carbon nanotubes” (in Nature 416, 495–496, Apr. 4, 2002).
Another method for controlling the direction of growth of single-walled carbon nanotubes by means of electric fields was reported in an article by Yuegang Zhang et al. title “Electric-field-directed growth of aligned single-walled carbon nanotubes” (Applied Physics Letters, Vol. 79, Nov. 5, 2001).
However, carbon nanotubes of all the carbon nanotube based structures obtained by the above-mentioned methods are aligned along a linear direction, and/or extend perpendicularly from the substrates. Furthermore, the idea of using external electric-fields to direct the carbon nanotube's growth is not suitable to build complicated structures wherein the carbon nanotubes bend in several directions.